The inverter is mainly composed of semiconductor power devices and inverter drive and control circuits. With the rapid development of microelectronics technology and power electronics technology, the emergence of new high-power semiconductor switching devices and drive and control circuits has promoted the rapid development and technological improvement of inverters. Current inverters mostly use a variety of advanced and easy-to-control high-power devices such as power field effect transistors (VMOSFET), insulated gate transistors (IGBT), gate turn-off transistors (GTO), MOS control transistors (MGT), MOS control thyristors (MCT), electrostatic induction transistors (SIT), electrostatic induction thyristors (SITH), and intelligent power modules (IPM). The control inverter drive circuit has also developed from analog integrated circuit to single-chip control, and even adopts digital signal processor (DSP) control, which makes the inverter develop in the direction of high frequency, energy saving, intelligence, integration and multi-function.
The main components of the inverter
(1) Semiconductor power switching device
The semiconductor power switching devices commonly used in inverters mainly include thyristors, high-power transistors, power field effect transistors, and power modules.
(2) Inverter drive and control circuit
The traditional inverter circuit is composed of many separate components and analog integrated circuits. This circuit structure has a large number of components, poor waveform quality, and cumbersome and complex control circuits. With the requirements for high efficiency and large capacity of inverter technology and the increasing complexity of inverter technology, the amount of information that needs to be processed is increasing. The development of microprocessors and special circuits have met the requirements of inverter technology development.
① Inverter drive circuit. The inverter drive circuit of the photovoltaic system inverter is mainly aimed at the drive of power switching devices. To obtain a good PWM pulse waveform, the design of the drive circuit is very important. With the development of microelectronics and integrated circuit technology, many application-specific multi-function integrated circuits have been launched one after another, which has brought great convenience to the design of application circuits, and also greatly improved the performance of the inverter. For example, various switch drive circuits SG3524, SG3525, TL494, IR2130, TLP250, etc., are widely used in inverter circuits.
②Inverter control circuit. The commonly used control circuits in photovoltaic inverters mainly provide logic and waveforms that meet the requirements for the drive circuit, such as PWM, SPWM control signals, etc., from 8-bit microprocessors with PWM ports to 16-bit single-chip microcomputers, up to 32 DSP devices and so on. So that advanced control technology such as vector control technology, multi-level conversion technology, repetitive control technology, fuzzy logic control technology, etc. have been applied in the inverter. Microprocessor circuits commonly used in inverters include MP16, 8XC196MC, PIC16C73, 68HC16, MB90260, PD78366, SH7034, M37704, M37705, etc. Commonly used dedicated digital signal processor (DSP) circuits include TMS320F206, TMS320F240, M586XX, DSPIC30, ADSP-219XX, etc.